The overall goal of the Principal Research Core (PRC) of the Advanced Center to Improve Pediatric Mental Health Care (ACIPMHC) is to conduct effectiveness and implementation research that informs improvement of pediatric mental health care in the public service sectors of child welfare and mental health, by achieving greater integration of evidence-based practices (EBPs) and usual care. The research program is built upon a 17 year history of clinical epidemiology studies, and a more recent set of effectiveness and implementation studies conducted in a collaboration between services researchers in San Diego and intervention researchers at the Center for Research to Practice (CR2P: linked to the Oregon Social Learning Center) in Oregon, as well as with other intervention researchers across the country who are involved with parent-mediated interventions for youth with externalizing behavior problems/disruptive behavior disorders. Interventions central to existing and proposed studies include: The Incredible Years (Webster-Stratton), Parent-Child Interaction Therapy (Eyberg), Multidimensional Treatment Foster Care/Parent Management Training (Chamberlain, Fisher, Reid), and Multisystemic Therapy (Henggeler, Schoenwald). The overall PRC goal will be addressed through two specific aims: 1) To use an interdisciplinary research network linking intervention and services researchers to develop effectiveness and implementation research on strategies to integrate EBP and usual care to improve children's MH care. The core uses a multiple-stakeholder framework emphasizing community and organizational contexts, interchange of multiple perspectives, diverse methods of multi-level research spanning qualitative and quantitative traditions, and emerging theoretical frameworks. 2) To conduct developmental and pilot studies that inform full-scale effectiveness and implementation studies in the CW and MH sectors. The PRC will link investigators from different methodological and conceptual approaches and will link closely to proposed workgroups in the RMC as well as the CMC Board to conduct studies in collaboration with community stakeholders in natural laboratories at the local, state and national levels. Two developmental studies and two small pilot studies are proposed to demonstrate the type and scope of work intended in this core.